1. Field of the Invention
The present invention generally relates to a structure that may be used for micro reaction or analysis in a bio Micro Electro Mechanical System (MEMS), and more particularly, to a plastic microfabricated structure for a bio chip, and a microfabricated thermal device, a microfabricated reactor, a microfabricated reactor array and a micro array using the same, which employ plastic that has high flatness, thermal isolation, and small thermal mass.
2. Discussion of Related Art
In general, a bio MEMS device, in particular, a lab-on-a-chip for medical and disease diagnosis using DNA allows a real time diagnosis to be performed, so that many researches are conducted to implement its small size and low cost. Preference is made to general purpose medical diagnosis equipment such as single use type. As a result, attentions are moved from materials such as silicon and glass to plastics which require a relatively low cost in recent years.
A high temperature is required to process DNA in a DNA lab-on-a-chip. In particular, a temperature of about 40° C. to 100° C. is required for cell lysis, DNA amplification (mainly, polymerase chain reaction (PCR)), reaction control, fluid transport, and so forth. In recent years, many microfabricated thermal devices are developed for the above-mentioned process, however, the silicon and glass are mainly employed for material of the devices.
In particular, a short analysis time is required for the real time diagnosis and low power consumption to be suitable for portable battery in a case of lab-on-a-chip. To that end, the structure should be designed and fabricated to allow thermal isolation and have small thermal mass. Conventional structures have been fabricated by semiconductor process technique employing silicon as their materials because the process technique is well established and allows a micro pattern to be formed. For example, thermal circulation devices having several chambers are fabricated using silicon etching. (See U.S. Pat. No. 5,589,136 (December 1996) to Northrup et al and U.S. Pat. No. 5,716,842 (February 1998) to Baier Volker et al.) When these techniques are employed, a thermal heater may be implemented for all reaction chambers, however, it is difficult to remove thermal cross-talk due to thermal isolation properties between reaction chambers. Thus, it has a difficulty in applying for chambers which separately have an independent temperature circulation rule. In addition, performance of devices is superior because they use a silicon material, however, it requires an extremely clean laboratory and high cost equipment capable of performing semiconductor processes, which causes fabrication cost and time to be increased, and makes it hard to apply for a single use medical diagnostic device.
A system in which a capillary electrophoresis (CE) device and a reaction chamber are combined is fabricated using a glass substrate, and PCR (DNA amplification) is performed on the glass substrate. (See Analytic Chemistry Paper, R.A. Mathies group of UC Berkeley, entitled “Single-molecule DNA amplification and analysis in an integrated microfluidic device”, Feb. 1, 2001.) However, this technique makes it hard to process the glass substrate and fabricate a heating thin layer having a small thermal mass. As a result, power consumption is high and reaction speed is slow, which causes an additional Proportional Integrated Differential (PID) controller to be attached to.
As such, there exists a need for obtaining another device, which has thermal properties such as that of silicon or glass, facilitates a process, and allows it to be fabricated at a low cost.
Plastic in the lab-on-a-chip is significantly limited to be used for fabricating the structure such as fluid path, channel, and chamber among micro-fluidic devices. However, the plastic has advantages of low cost, easy processing, and low thermal interference due to extremely low thermal conductivity. Nevertheless, the plastic microfabricated structure could not have been applied for a thermal device of the lab-on-a-chip for the disease diagnosis due to a lack of technique for fabricating a structure having heat resistance, compatibility to semiconductor process technique, substrate flatness, and small thermal mass. To cope with this problem, there exists a need for developing a technique capable of allowing heat resistance, flatness enough to allow a photolithography process to be performed, the material capable of being subject to stringent conditions of the semiconductor process, and capable of fabricating a microfabricated structure having a small thermal mass by employing the same.